1. Field of the Invention
The present invention relates to a piezoelectric film and a method of manufacturing same, and to a piezoelectric device and a liquid ejection apparatus, and more particularly to a piezoelectric film having improved piezoelectric performance and improved surface morphology and a method of manufacturing such a piezoelectric film, and to a piezoelectric device and a liquid ejection apparatus.
2. Description of the Related Art
A piezoelectric device which includes a piezoelectric body having piezoelectric characteristics whereby the body expands and contracts with increase and decrease in the intensity of an applied electric field, and electrodes through which the electric field is applied to the piezoelectric body, are used in applications such as piezoelectric actuators mounted in inkjet type recording heads. A perovskite type oxide, such as lead zirconate titanate (PZT), is used widely as piezoelectric material. The piezoelectric material is ferroelectric and possesses a spontaneous electric polarization when no electric field is applied.
It has been known since the 1960s that PZT that is doped with various donor ions having higher valence than the valence of the substituted ions has improved properties, such as ferroelectric characteristics, compared to pure PZT. V5+, Nb5+, Ta5+, Sb5+, Mo6+, Mg2+, W6+, and the like, are known as donor ions which substitute for Zr4+ and/or Ti4+ at the B site.
For example, Japanese Patent Application Publication No. 2005-333088 discloses a piezoelectric film in which, in order to provide a piezoelectric device having a high piezoelectric constant, at least one element of Zn, Ni, Mn and Mg, and at least one element of Nb and Ta are respectively combined at the B site in a ratio of 1:2.
However, a relaxor-type PZT, typically PMN-PZT having Mg and Nb for substitution at the B site, such as that described in Japanese Patent Application Publication No. 2005-333088, displays higher piezoelectric performance than normal PZT in bulk form, but does not yield high piezoelectric performance in the form of a thin film. Furthermore, when the relaxor-type PZT is formed as a thin film, there has been a problem in that the surface characteristics of the film are poor.